JPH01285917A - Rotating polygon mirror device - Google Patents

Abstract

PURPOSE:To reduce the size and weight of the rotating polygon mirror device by rotating the polygon mirror 5 around a hemispherical revolving shaft. CONSTITUTION:The hemispherical revolving shaft 4 is integrally molded to the revolution center of the polygon mirror 5 and spiral grooves 4a are formed on the surface thereof at the time of working said mirror. Magnets 7 are embedded in the polygon mirror 5 so as to enclose the revolving shaft 4. This revolving shaft 4 is sandwiched by an upper bearing 2 (provided with a hemispherical recess) and a lower bearing 3 and plural pieces of coils 6 are installed to enclose the circumferences of these bearings. A dynamic pressure is generated by the spiral grooves 4a formed on the revolving shaft 4 and the polygon mirror 5 starts rotating without contacting while the mirror is supported by the upper bearing 2 and the lower bearing 3 when the rotation of the polygon mirror 5 is started by the effect of the coils 6 supplied with current and the magnets 7. The thickness, size and weight of the polygon mirror are thereby reduced.

Description

Detailed Description of the Invention [Technical Field] The present invention relates to a rotating polygon mirror device used in an optical deflector of a laser printer, an optical measuring instrument, etc., and particularly relates to a holding structure thereof (
(hydrodynamic bearing structure).

[Prior art]

Hydrodynamic bearings conventionally used in rotating polygon mirrors include a shaft with a herringbone groove on the outer periphery, and a hollow cylindrical rotating shaft that is rotatably inserted into the outside of this shaft. The most well-known configuration is to attach a polygon mirror to the mirror.

However, in this configuration, high precision is required for both the shaft rotation axis and the surface roughness of roundness 5, which has the drawback of increasing processing costs.

Therefore, for example, in Japanese Patent Application Laid-open No. 61143715,
A structure has been proposed in which a rotating shaft having spherical bodies at both ends is rotatably supported by upper and lower bearings having concave spherical surfaces, and a polygon mirror is attached to the rotating shaft.

However, since a large force is applied in the thrust direction,
It was thought that this shape would not be able to support it, and it could not be said to be practical.

Further, with this configuration, it is difficult to make the device as a whole thin, and there is a limit to how small and lightweight the device can be made.

〔the purpose〕

SUMMARY OF THE INVENTION It is an object of the present invention to provide a rotating polygon mirror device that eliminates the drawbacks of the above-mentioned prior art and can be made smaller and lighter without incurring undue manufacturing costs.

〔composition〕

In order to achieve this object, the present invention provides a hemispherical rotating shaft at the center of both end faces of a polygon mirror, and also provides a pair of bearings that face this rotating shaft with a small distance therebetween, and Alternatively, a spiral groove is formed on the surface of the bearing.

Hereinafter, one embodiment of the present invention will be described based on the drawings.

FIG. 1 is a longitudinal sectional view of a rotating polygon mirror device according to an embodiment of the present invention, FIG. 2 is a plan view of its rotating shaft portion, and FIG. 3 is an external perspective view of the polygon mirror and lower bearing portion. .

In Fig. 1, 1 is a frame, 2 is an upper bearing, 3 is a lower bearing, 4 is a rotating shaft, 5 is a polygon mirror,
6 is a coil, 7 is a magnet, and 8 is a transparent window.

When processing the polygon mirror 5, a hemispherical rotating shaft 4 is integrally molded at the center of rotation, and a spiral groove 4a is formed on its surface as shown in FIG.

As shown in FIG. 3, a magnet 7 is embedded in the polygon mirror 5 so as to surround the rotating shaft 4. Aluminum, glass, ceramic, etc. can be used as the material for the polygon mirror 5, but in the case of aluminum, the rotating shaft 4 portion is plated with nickel or the like to provide wear resistance and rigidity. The rotating shaft 4 has an upper bearing 2 (with a hemispherical recess)
and the lower bearing 3. A plurality of coils 6 are installed so as to surround these bearings.

When the polygon mirror 5 into which the magnet 7 is inserted begins to rotate due to the action of the current-carrying coil 6 and the magnet 7, dynamic pressure is generated by the spiral 14a formed on the rotating shaft 4.
The polygon mirror 5 has an upper bearing 2. While being supported by the lower bearing 3,
Rotation can now be performed without contact.

Further, by using a type in which the magnet 7 is sandwiched between the upper and lower coils 6, the polygon mirror 5 is prevented from vertically rotating.

Although this embodiment shows the polygon mirror 5 that rotates in the horizontal direction, it can also be set to rotate in any direction including the vertical direction since it becomes non-contact when dynamic pressure is generated. .

〔effect〕

As described above, according to the rotating polygon mirror device according to the present invention, the polygon mirror is rotated around a hemispherical rotation axis, rather than a configuration in which a rotating body to which a polygon mirror is attached is fitted to a fixed shaft. Therefore, it is possible to make the device much thinner than the conventional device, and since the precision of parts is not required as in the conventional device, the processing cost can be reduced. Furthermore, since the rotating shaft is spherical, it can support both thrust and radial directions at the same time.
Also, there is no need for alignment.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view of a rotating polygon mirror device according to an embodiment of the present invention, FIG. 2 is a plan view of its rotating shaft portion, and FIG. 3 is an external perspective view of the polygon mirror and lower bearing portion. . 2.3... Upper and lower bearings, 4... Rotating shaft, 4a...
Spiral groove, 5...polygon mirror.

Claims (1)

[Claims] A hemispherical rotating shaft is provided at the center of both end faces of the polygon mirror, and a pair of bearings are provided that face the rotating shaft with a slight distance therebetween, and a spiral groove is formed on the surface of the rotating shaft or the bearing. A rotating polygon mirror device featuring: